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Comparison on Thermodynamic Performances between Basic and Regenerative Sub-Critical Organic Rankine Cycles Coupled with Low Grade Heat Source

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IOP Conference Series: Materials science and Engineering 2019年第1期473卷

作者： Pengfei Yuan Chao Zhang Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control 300384 Tianjin China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education (Tianjin University of Technology) Tianjin 300384 China

The coupling effects of low grade heat source on thermodynamic performances of both the basic and regenerative sub-critical Organic Rankine cycle (ORC) systems are investigated and compared. Turbine inlet pressure and turbine inlet temperature are treated as independent variables. The system exergy efficiency is selected as the thermodynamic performance criterion. The waste hot water with temperature range of 373.15K to 423.15K is selected as the low grade heat source. Optimization studies are carried out by using eight common organic working fluids to recover heat energy, and relevant operating conditions are obtained respectively. The results indicate that both hot fluid inlet temperature and the allowable minimum hot fluid outlet temperature influence the optimal working fluid, relevant turbine inlet condition and system exergy efficiency. Optimal system exergy efficiency increases monotonously with increasing of hot fluid temperature for both ORC systems above. In comparison to the basic cycle configuration, optimal system exergy efficiency for the regenerative system using the same working fluid is not changed if relevant turbine inlet vapor is saturated, but is significantly improved if relevant turbine inlet vapor is overheating. Besides, the optimal working fluid is dependent on the heat source temperature and specific cycle configuration.

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Flow Mechanism of Cooling Effectiveness Improvement for the Cylindrical Film Cooling Hole with Contoured Craters

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IOP Conference Series: Materials science and Engineering 2019年第1期473卷

作者： Linchao Bai Chao Zhang Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control 300384 Tianjin China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education (Tianjin University of Technology) Tianjin 300384 China

In this paper, a typical cylindrical hole with contoured craters is investigated in terms of the downstream flow field by numerical method at blowing ratios of 0.5, 1 and 1.5. The flow field and the cooling effectiveness are analyzed using three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. In comparison to the cylindrical hole, the cratered hole shows a wider coolant coverage in lateral direction and a lower penetration into the mainstream flow due to the larger hole exit area. Moreover, the interaction between the coolant and the curved protrusion induces a new anti-kidney-shaped vortex pair, which can obviously improve the cooling coverage and thus the cooling effectiveness. The area-averaged cooling effectiveness for the cratered hole is always higher than that for the cylindrical hole at all three blowing ratios.

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Smart radio environments

arXiv

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arXiv 2021年

作者： Gradoni, Gabriele Renzo, Marco Di Díaz-Rubio, Ana Tretyakov, Sergei A. Caloz, Christophe Gradoni, Gabriele Peng, Zhen Alu, Andrea Lerosey, Geoffroy Fink, Mathias Galdi, Vincenzo Cui, Tie Jun Frazier, Benjamin W. Anlage, Steven M. Salucci, Marco Massa, Andrea Cheng, Qiang Wang, Jinghe Jin, Shi Dardari, Davide Decarli, Nicoló Yurduseven, Okan Matthaiou, Michail Kenney, Mitchell Gordon, George Georgiou, Orestis Nguyen, Cam Ly Martini, Enrica Maci, Stefano Wakatsuchi, Hiroki Phang, Sendy School of Mathematical Sciences Department of Electrical and Electronic Engineering University of Nottingham Nottingham United Kingdom Laboratoire des Signaux et Systémes CNRS CentraleSupélec Université Paris-Saclay Gif-sur-Yvette Paris France Department of of Electronics and Nanoengineering Aalto University Espoo Finland META Research Group KU Leuven Belgium School of Mathematical Sciences Department of Electrical and Electronic Engineering University of Nottingham University Park NG72RD United Kingdom Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign IL United States Advanced Science Research Center City University of New York United States Greenerwave 6 rue Jean Calvin Paris75005 France Institut Langevin 1 rue Jussieu Paris75005 France Fields & Waves Lab Department of Engineering University of Sannio Benevento Italy State Key Laboratory of Millimeter Waves Southeast University Nanjing China Applied Physics Laboratory Johns Hopkins University LaurelMD20723 United States Department of Electrical and Computer Engineering Department of Physics Quantum Materials Center University of Maryland College ParkMD20742 United States Trento Italy Chengdu China Beijing China Institute of Electromagnetic Space State Key Laboratory of Millimeter Waves Southeast University Nanjing210096 China National Mobile Communications Research Laboratory Southeast University Nanjing China University of Bologna Bologna Italy Bologna Italy Centre for Wireless Innovation Institute of Electronics Communications and Information Technology Queen’s University Belfast Belfast United Kingdom Department of Electrical and Electronic Engineering University of Nottingham Nottingham United Kingdom Department of Electrical and Computer Engineering University of Cyprus Nicosia Cyprus Wireless System Laboratory Corporate Research & Development Center Toshiba Corporation Kawasaki Japan Department of Information Engineering an

This Roadmap takes the reader on a journey through the research in electromagnetic wave propagation control via reconfigurable intelligent surfaces. Meta-surface modelling and design methods are reviewed along with physical realisation techniques. Several wireless applications are discussed, including beam-forming, focusing, imaging, localisation, and sensing, some rooted in novel architectures for future mobile communications networks towards 6G. © 2021, CC BY.

关键词： Electromagnetic wave propagation

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Rhombohedral Sb2Se3 as an intrinsic topological insulator due to strong van der Waals interlayer coupling

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Physical Review B 2018年第7期97卷 075147-075147页

作者： Guohua Cao Huijun Liu Jinghua Liang Long Cheng Dengdong Fan Zhenyu Zhang Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education and School of Physics and Technology Wuhan University Wuhan 430072 China International Center for Quantum Design of Functional Materials (ICQD) Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics University of Science and Technology of China Hefei Anhui 230026 China

Three-dimensional topological insulators (TIs) are a new class of quantum materials that have insulating energy gaps in bulk form but exhibit robust gapless surface states protected by time-reversal symmetry. It was theoretically predicted and experimentally confirmed that the binary tetradymites Bi2Te3, Bi2Se3, and Sb2Te3 are all TIs, while the fourth system out of the 2 × 2 combination, Sb2Se3, was prevailingly believed to be topologically trivial due to its relatively weak spin-orbit coupling (SOC). In this paper, we demonstrate through a comparative first-principles study that Sb2Se3 is actually also an intrinsic TI, as characterized by its topologically protected surface states and Z2 invariant. The underlying reason is the inclusion of the ubiquitous van der Waals attraction between the quintuple layers, effectively narrowing the bulk band gap, allowing the SOC effect to induce a band inversion around the Fermi level. This paper also points to the importance of the seemingly weak dispersion forces in defining the topological properties of quantum materials.

关键词： Electronic structure Topological insulators Van der Waals interaction First-principles calculations

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Hard Carbon Aerogels: Superelastic Hard Carbon Nanofiber Aerogels (Adv. Mater. 23/2019)

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Advanced Materials 2019年第23期31卷

作者： Zhi‐Long Yu Bing Qin Zhi‐Yuan Ma Jin Huang Si‐Cheng Li Hao‐Yu Zhao Han Li Yin‐Bo Zhu Heng‐An Wu Shu‐Hong Yu Division of Nanomaterials & Chemistry Hefei National Laboratory for Physical Sciences at the Microscale CAS Center for Excellence in Nanoscience Hefei Science Center of CAS Department of Chemistry University of Science and Technology of China Hefei 230026 China CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern Mechanics CAS Center for Excellence in Complex System Mechanics University of Science and Technology of China Hefei 230027 China

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Near-Optimal Online Motion Planning of Connected and Automated Vehicles at a Signal-Free and Lane-Free Intersection

Near-Optimal Online Motion Planning of Connected and Automat...

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2018 IEEE Intelligent Vehicles Symposium, IV 2018

作者： Li, Bai Zhang, Youmin Zhang, Yue Jia, Ning Ge, Yuming Shaanxi Key Laboratory of Complex System Control and Intelligent Information Processing Xi'An University of Technology Xi'an710048 China College of Control Science and Engineering Zhejiang University Hangzhou310027 China Department of Mechanical Industrial and Aerospace Engineering Concordia Institute of Aerospace Design and Innovation Concordia University Montreal Canada Division of Systems Engineering Center for Information and Systems Engineering Boston University BostonMA02215 United States Institute of Systems Engineering Tianjin University Tianjin300072 China China Academy of Information and Communications Technology Beijing100191 China

ISBN: (纸本)9781538644522

In this paper, we propose a cooperative motion planning method for a group of connected and automated vehicles (CAVs) crossing a lane-free intersection without using explicit traffic signaling. This multi-vehicle motion planning task is formulated as a centralized optimal control problem. However, the solution to this optimal control problem is numerically intractable due to the high dimensionality of the collision-avoidance constraints and the nonlinearity of the vehicle kinematics. A two-stage strategy is proposed for generating online solutions: at Stage 1, the CAVs are requested to reach a standard formation before entering the intersection;at Stage 2, the vehicles cross the intersection. As the motion planning sub-problem at Stage 2 begins with a standard configuration, the optimal solution to this standard sub-problem can be computed offline in advance and applied online directly. On the other hand, the formation reconfiguration sub-problem at Stage 1 is easy to solve online. Through dividing the entire dynamic process into two periods, the difficulties in the original optimal control problem are significantly reduced so that the real-time performance is achieved. © 2018 IEEE.

关键词： Motion planning

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A Fluid-Filled Tubular Dielectric Elastomer Variable Stiffness Structure Inspired by the Hydrostatic Skeleton Principle

A Fluid-Filled Tubular Dielectric Elastomer Variable Stiffne...

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IEEE International Conference on Robotics and Automation

作者： Tao Wang Yue Li Yuanjie Li Jinhua Zhang Jun Hong Michael Yu Wang Key Laboratory of Education Ministry for Modern Design & Rotor-Bearing System Xi'an Jiaotong University Xi'an Shaanxi China Department of Mechanical and Aerospace Engineering & Department of Electronic and Computer Engineering Hong Kong University of Science and Technology Kowloon Hong Kong

This work presents a novel variable stiffness structure consisting of a fiber-constrained dielectric elastomer tube filled with insulating oil. The tensile stiffness of the structure can be adjusted by voltages and its initial value can be customized according to the initial pre-stretch of the material. The structure has a dimension of ～30 mm diameter ×50 mm length. A mathematical analysis is established to predict the initial tensile stiffness of the structure. The changes of the tensile stiffness of the structure under voltages are verified experimentally. The results show a decrease of the tensile stiffness of the device by 25% at 4 kV and the decrement is also related to the elongation of the structure. With different pre-stretches and dimensions of the dielectric elastomer, one can obtain devices with different variation ranges of tensile stiffness.

关键词： Electron tubes Strain Oils Muscles Hydraulic systems Force Soft robotics

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Development of high-strength,low-cost wrought Mg–2.0 mass% Zn alloy with high Mn content

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Progress in Natural science:Materials International 2016年第6期26卷 630-635页

作者： Fusheng.Pan Jianjun Mao Gen Zhang Aitao Tang Jia She College of Materials Science and Engineering Chongqing University National Engineering Research Center for Magnesium Alloys Chongqing University Chongqing Research Center for Advanced Materials Chongqing Academy of Science and Technology Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China

Mg–Zn–Mn-based alloys have received considerable attention because of their high creep resistance, strength,and good corrosion resistance. The alloying element Mn in Mg–Zn-based alloys is commonly less than 1 wt%. In the present study, the effect of high Mn content(1 wt% and 2 wt%) on the microstructures and mechanical properties of Mg–2Zn–0.3Sr extruded alloy was investigated. The results revealed that the high Mn content significantly increased the ultimate tensile strength, tensile yield strength, compress yield strength, and yield asymmetry of the alloy without affecting its ductility. The dynamically recrystallized(DRXed) grains of Mg–2Zn–0.3Sr were remarkably refined because of the large amount of fine Mn precipitates in the homogenized alloy. The improved strengths were mainly attributed to the fine DRXed grains according to the Hall–Petch effect and to the large amount of spherical and < 0001 > Mn precipitates through the precipitation and dispersion strengthening. The fine DRXed grains and numerous Mn precipitates effectively suppressed the extension twining, substantially enhanced the compress yield strength, and resulted in improved anisotropy.

关键词： Magnesium alloy Mg–Zn alloy Microstructure Ultra-fine grains Second phase Mechanical properties

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Unified Rendering Array Driver Runtime Optimization for Graphic Application

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IOP Conference Series: Earth and Environmental science 2019年第1期234卷

作者： Chengcheng Ma Ze Tian Honghong Liu Zhao Nie China Aeronautical Computing Research Institute Aviation key Laboratory of Science and Technology on integrated Circuit and Micro-System Design P.O. Box 710068 China Xiangteng microelectronics technology co. LTD P.O. Box 710068 China

As the core of GPU processing, the performance of Unified rendering array is directly affected by the shader driver. On the basis of research the structure of Unified rendering array processing, this paper proposes a runtime Unified rendering array driver optimization method for graphical application, can according to different graphics application scenario runtime to generate optimized Unified rendering array driver, testing on graphics processors FPGA verification environment, driven by the runtime optimization compared with the traditional full function driver, performance increased by 55% - 270%.

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Future prospect of solar sails by comparing two light propulsion sailing schemes 21

Future prospect of solar sails by comparing two light propul...

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21st AIAA International Space Planes and Hypersonics Technologies Conference, Hypersonics 2017

作者： Jiang, Li Shi, Aiming Qin, Zhixuan NPU-Duke Joint Research Laboratory for Light Pressure Propulsion Solar Sail-Craft Dynamics National Key Laboratory of Science and Technology on Aerodynamic Design and Research Northwestern Polytechnical University National Key Laboratory of Aerodynamic Design and Research Box 114 No.127 West Youyi Road Xi’anShaanxi710072 China

ISBN: (数字)9781624104633

ISBN: (纸本)9781624104633

The concept of solar sailing using sunlight propelling thin membrane structure has been proposed for a long time. The principle of this technology is accumulating velocity to reach a very high speed which may up to 10% speed of light based upon the fact that object could be consistently accelerated even by a tiny force in outer space environment. In 2010, solar sailing was confirmed by IKAROS of JAXA. In this paper, two kinds of propulsive mechanism are mentioned. One propulsive way is based upon the momentum exchange of photons and solar sails. The other propulsive scheme which uses special-made graphene material emitting electrons exhibits a great potential. The former scheme based upon momentum exchange is relatively persistent and stable but requires a large reflecting surface area at the same time. The latter scheme could provide a several orders larger propulsive force although there are engineering difficulties need to be overcome. The values of acceleration due to two propulsive schemes respectively are compared to illustrate the propulsive efficiency. It is believed that if the latter technology matures and these two propulsive ways could be combined comprehensively, a combined light propelling system with better performance would be possible in the future. © 2017, American Institute of Aeronautics and Astronautics Inc, AIAA. All rights reserved.

关键词： Solar sails

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